In general a sliding vane type compressor comprises, as shown in FIG. 1, a cylinder 1 having interior cylindrical space, side plates (not shown in FIG. 1) which are fixed to both side faces of the cylinder and close tightly a vane chamber 2 in the interior space of the cylinder at its side faces, a rotor 3 arranged eccentrically within the cylinder 1, and vanes 5 engaged slidably in grooves 54 provided on the rotor 3. Further, reference numeral 6 designates a suction port formed in the side plate, and 7 designates a discharge hole formed in cylinder 1. The vanes 5 move outwardly due to centrifugal force upon rotation of the rotor 3, and the end edges slide on the interior wall surface of cylinder 1, thereby to prevent passage of gas in the compressor thereby.
In a rotary compressor such as a sliding vane type, a small and simple structure is possible compared with the reciprocating type compressor which is complex in its structure and which has many parts, so it has recently come to be used as an automobile refrigerant compressor. However, in this rotary type compressor, there are such problems as described hereinafter compared with the reciprocating type.
In the case of the automobile refrigerant compressor, the driving force of the automobile engine is transmitted to a pulley of a clutch through a belt, and it drives a rotary shaft of the compressor. Accordingly, when the sliding vane type compressor is used, its compression action rises in a proportion to the rotational speed of the engine of the automobile.
On the other hand, when a conventional reciprocating type comporessor has been used, the follow-up property of the suction valve becomes bad in the high rotational speed range, and gas to be compressed cannot be sucked fully into the cylinder, and as the result, compression of refrigerant is automatically reduced in the high rotational speed range, while in the rotary type compressor, there is no such action, and compression efficiency is decreased due to increasing compression work, or it reaches an over-cooling state. As a method to overcome the aforesaid problems in the rotary compressor, it has been proposed to provide a control valve to vary the cross-sectional area of the intake passage communicated with the suction port 6 of the rotary compressor, and control is performed by throttling the area in the high speed range and utilizing the suction loss. However, in this case, there is a problem that such a control valve must be added to the existing apparatus, which makes the construction become complex and the cost high. As another method to overcome over-compression of the rotary compressor in the high speed range, there has been proposed hitherto a construction in which the rotational speed is not increased over a certain value by using a fluid clutch, planetary gears, etc.
However, in the former arrangement, energy loss due to frictional heat generated by relatively moving faces is large, and in the latter arrangement the dimensions and shape of the apparatus become large due to the addition of the planetary gear mechanism having a large number of parts, whereby both arrangements are difficult to utilize practically where simplification and compactness are increasingly required and the trend toward energy-saving is increasing.
The present inventors have investigated in detail the phenomena of pressure in the vane chamber when the rotary compressor is used in order to overcome the problems in the refrigeration cycle of an air conditioner for a motor vehicle, and as a result, it has been found that self-restraining action of the refrigeration capacity in the high speed rotation range can be effectively achieved for a rotary compressor, similarly to the conventional reciprocating compressor, by selecting and combining parameters such as the area of the suction port, quantity of refrigerant discharged, the number of vanes, etc.
The present invention relates to improvements in rotary compressor, and it provides a fundamental construction of a compressor which provides the ability control the compressing function more effectively in a compressor having many vanes (e.g. three-vanes or four-vanes).
In order to provide small torque variation in a compressor due to pulsations caused by the flow of discharged refrigerant and to attain a good operating feeling, a compressor having many vanes is preferable.
In a refrigeration cycle for a large car, a compressor having a large discharge capacity is required, and for a compressor having high reliability and no excessive over-compression pressure in the range of high speed rotation, such as more than 5000 rpm, it is better to have a larger number of vanes because the quantity of refrigerant discharged per vane chamber becomes small.
On the other hand, in the control of a compressor having many vanes, there is a problem that refrigerant in two or more vane chambers positioned before and behind a given vane interferes mutually during a suction stroke, so that full control of the compressive ability cannot be achieved.
Disclosure of the Invention
The present invention provides a fundamental contruction to control compression in a rotary compressor which overcomes said problems, and which has succeeded in gaining control equivalent to that obtainable in, e.g. a two van type compressor, by providing at least two suction ports so that refrigerant flowing into an individual vane chamber is supplied from each suction port independently.